Logical Reasoning

PT140 · S2 · Q24 Biologist: Scientists have discovered

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Biologist: Scientists have discovered fossilized bacteria in rocks 3.5 billion years old.

Conclusion (this suggests that)

Life may be able to arise under many difficult conditions throughout the universe.

Intermediate Conclusion (so)

The first life on Earth must have appeared soon after the planet's formation, when conditions were harsh.

Evidence

Earth is only 4.6 billion years old, and we've found fossils 3.5 billion years old, and ...

Intermediate Conclusion (so)

Those fossilized organisms had already had a long evolutionary history.

Evidence

These bacterial organisms were quite complex.

Evaluate

We have multiple so's, which always indicate a conclusion. And we have a this suggests that, which also indicates a conclusion.

In order to figure out which one is the Main conclusion, we can think about which ideas support the other, or we can just think about how these indicator words show us which claim is supporting which.

Scientists have discovered.... background fact The fossils indicate that ... conclusion based on claim 1 and so must have ... conclusion based on claim 2 However, Earth is 4.6 old ... pivoting into main argument with a fact so, the first life ... conclusion based on claim 4 This suggests that that life ... conclusion based on claim 5

The claim they're asking us about claim 3.

24.

Which one of the following most accurately describes the role played in the biologist's argument by the claim that the fossilized bacteria discovered in rocks 3.5 billion years old must have had a long evolutionary history?

  1. It is a claim for

    Contradicted: no support provided

    We can stop reading this after the 1st half. Any claim prefaced by "so" definitely had support provided. Why should we believe that [these fossilized bacteria had already had a long evolutionary history]? Because, they are quite complex. (It takes natural selection many, many generations of mutations and natural selection to create complex structures)

    6% picked this

  2. It is a claim for

    Contradicted: no support provided

    We can stop reading this after the 1st half (2nd half does seem legit, for what it's worth). Any claim prefaced by "so" definitely had support provided. Why should we believe that [these fossilized bacteria had already had a long evolutionary history]? Because, they are quite complex. (It takes natural selection many, many generations of mutations and natural selection to create complex structures)

    23% picked this

  3. Correct

    It is a claim for

    Why this is right

    This answer choice describes a sequence of four ideas. A claim supports OUR claim. Our claim supports some other intermediate conclusion, which supports the main conclusion. This is that chain of ideas in order: 1. The bacteria were quite complex so, 2. They already had a long evolutionary history 3.5 billion years ago so, 3. There was apparently already life on Earth soon after the planet formed (4.6 million years ago, when conditions were harsh) so, 4. Life may be able to arise under many harsh conditions.

    Skill tested: Role · how this choice captures the argument's function is the move to repeat next time.

    61% picked this

  4. It is a claim for

    Bad 2nd Half

    There was support provided for our claim (after all, it's prefaced by "so"), but our claim was part of supporting the eventual conclusion that "life appeared on Earth soon after its formation". The author is thinking that in order for complex life to be found by 3.5 billion years ago, it would have needed to get started way before that. Like, if it takes 1 billion years of evolution to result in life forms as complex as that bacteria, then finding this bacteria existing 3.5 billion year ago, then apparently life started evolving at least 4.5 billion years ago. The author isn't being that specific, but this is the sort of thinking that's leading the author to conclude that life must have appeared soon after the planet's formation.

    7% picked this

  5. It is a claim for

    Bad 2nd Half

    This is similar to (C), only it's saying that the last two claims (the two conclusions supported by our claim) are not related to each other; they're distinct. But we know that claim 5 and claim 6 (the last two in the paragraph) are not distinct. They're connected. After all, the author tells us claim 5 and then says This suggests that to lead into claim 6.

    4% picked this

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